Antenna device and electronic apparatus

Abstract

A first radiation electrode is formed on a bottom surface of a no-ground conductor formation area of a board, and second radiation electrodes are formed on a top surface of the no-ground conductor formation area. A longitudinal electrode of the first radiation electrode is electrically continuous with a ground conductor. A first end portion and a second end portion of a transverse electrode of the first radiation electrode extend toward the ground conductor. The transverse electrode of the first radiation electrode operates as a radiation element for radiating a signal at a first frequency. The second radiation electrodes each operate as a radiation element for radiating a signal at a second frequency, and also as a capacitive feed electrode for the first radiation electrode. This enables to strengthen directivity toward an antenna portion side (forward direction) of the board, and further enables multiband use.

The invention claimed is: 
     
       1. An antenna device including a board having a ground conductor formation area in which a ground conductor is formed and a no-ground conductor formation area in which no ground conductor is formed, said antenna device comprising
 a first radiation electrode and a second radiation electrode in the no-ground conductor formation area, the first radiation electrode being T-shaped and including a transverse electrode extending in a first direction and a longitudinal electrode protruding from a point between two end portions of the transverse electrode in a direction orthogonal to the first direction, the second radiation electrode being arranged near the transverse electrode of the first radiation electrode, 
 the first radiation electrode having a length configured to operate as a radiation element for radiating a signal at a first frequency, 
 the longitudinal electrode of the first radiation electrode being electrically continuous with the ground conductor or facing the ground conductor over a slit, 
 the first radiation electrode being disposed at a location so that a capacitance is formed between the ground conductor and an end portion of a transverse electrode of the first radiation electrode, 
 the second radiation electrode having a length configured to operate as a radiation element for radiating a signal at a second frequency which is higher than the first frequency, 
 the second radiation electrode being connected to a feed port, and 
 the second radiation electrode forming a capacitance with the first radiation electrode and performing capacitive feeding of a signal at the first frequency for the first radiation electrode. 
 
     
     
       2. The antenna device according to  claim 1 , wherein
 the first radiation electrode is formed on a first surface of the board, and the second radiation electrode is formed on a second surface thereof. 
 
     
     
       3. The antenna device according to  claim 1 , wherein
 a stub extending from the ground conductor is formed on a surface of the board opposite to the first radiation electrode. 
 
     
     
       4. The antenna device according to  claim 1 , wherein
 the second radiation electrode is disposed at a location so that a capacitance is formed between the second radiation electrode and the longitudinal electrode of the first radiation electrode. 
 
     
     
       5. The antenna device according to  claim 1 , wherein
 the no-ground conductor formation area includes two units of the second radiation electrode, and the two units of the second radiation electrode are connected to individual feed ports, 
 the two units of the second radiation electrode each form a capacitance with the first radiation electrode, and each perform capacitive feeding of the signal at the first frequency for an end portion of the transverse electrode of the first radiation electrode. 
 
     
     
       6. An electronic apparatus including the antenna device according to  claim 1 , wherein
 the antenna device is stored inside the electronic apparatus so that a direction from the ground conductor formation area to the transverse electrode of the first radiation electrode matches a forward direction of the electronic apparatus.